The present invention relates to a hydraulically operated continuously variable transmission, and more particularly to a hydraulically operated continuously variable transmission having a single oil cooling unit for dissipating the heat generated by the various sliding surfaces in the transmission.
Hydraulically operated continuously variable transmissions are known in the art as disclosed in Japanese Laid-Open Patent Publication No. 57-76357, for example.
Such hydraulically operated continuously variable transmissions have various members or locations which generate heat due to power loss. These heat-generating members may be associated with respective oil cooling units for cooling oil that has absorbed generated heat.
The hydraulically operated continuously variable transmission has a hyraulic motor including a motor cylinder, a hydraulic pump including a pump cylinder and a pump swash plate rotatable with the motor cylinder, a distribution ring, and a distribution member slidably held against the distribution ring. Since pump swash plate rotates with the motor cylinder, the amount of heat generated by the hydraulic pump is greater as the differential rotational speed between the pump cylinder and the motor cylinder is higher, i.e., the output rotational speed of the transmission is lower. The amount of heat produced by the sliding surfaces of the distribution ring and the distribution member is high as the output rotational speed is relatively high because the rotational speed of the distribution member is in proportion to the output rotational speed.
Therefore, the maximum heat generated by the sliding surfaces in the hydraulic pump and the maximum heat generated by the sliding surfaces of the distribution ring and the distribution member are not produced at the same time, and therefore could be dissipated by a single oil cooling unit.